Intumescent Flame Retardant Composites Research Articles

Surface modification of bamboo fibers by diammonium phosphate and their applications in flame retardant thermoplastic polyurethane

AbstractBamboo fibers (BF) were used as charring agent in thermoplastic polyurethane (TPU), together with ammonium polyphosphate (APP) to prepare intumescent flame retardant composites. In order to improve the dispersibility and flame retardant efficiency, BF was grafted with diammonium phosphate (DAP), named as modified bamboo fibers (M‐BF). By the presence of 8 wt% APP and 2 wt% M‐BF, the sample could achieve the maximal limiting oxygen index (LOI) value of 30.5% and V‐0 rating in UL‐94 test. The peak heat release rate for TPU/8APP/2 M‐BF is 190 kW/m2, which is 86.0% lower than that of neat TPU. Besides, TPU/8APP/2 M‐BF sample presented a tensile strength of 23.0 MPa, which was slightly lower than neat TPU sample. The thermogravimetric analysis for TPU composites and the morphology observation of the char demonstrated that APP and M‐BF took effects on condensed phase through promoting the formation of intumescent char structure and free radical trapping. Meanwhile, it could release inert gases in gas phase. Therefore, M‐BF exhibited great potential in applying as renewable charring agent for alleviating the depletion of petroleum resources.

Synergistic effect of layered melamine-phytate and intumescent flame retardant on enhancing fire safety of polypropylene

The possibility of layered melamine-phytate (MEL-PA) as an efficient synergist for intumescent flame retardant (IFR) is explored. The synergistic effects of MEL-PA on polypropylene (PP)/IFR composites are investigated in terms of flammability tests and combustion under forced-flaming condition. The addition of MEL-PA can effectively improve limited oxygen index (LOI) of PP composites. When 2 mass% MEL-PA is incorporated, the LOI value is enhanced from 33.0 to 35.1%. In addition, fire-retardant performance is increased with the addition of MEL-PA. The heat and smoke releases of PP/IFR are greatly reduced by MEL-PA. When IFR is partially replaced by 0.5, 1.0 and 2.0 mass% MEL-PA, total smoke production values are decreased by 27.2%, 34.8% and 57.6%, respectively. Raman spectra analysis indicates that the adding of MEL-PA results in higher graphitization degree of char layer. This work proves that MEL-PA and IFR have a good synergistic effect on flame-retardant PP.

Synergistic effect of zeolite 4A on thermal, mechanical and flame retardant properties of intumescent flame retardant HDPE composites

The combination of synergistic agent with intumescent flame retardant (IFR) systems provides a promising way to prepare high performance IFR composites. In this study, the effects of the synthetic zeolite 4 A in combination with the IFR system consisting of ammonium polyphosphate (APP) and tris (2-hydroxyethyl) isocynurate (THEIC) on thermal degradation, mechanical properties, flame retardancy and char formation of high-density polyethylene composites were investigated by limiting oxygen index (LOI) measurement, cone calorimetry, scanning electron microscopy and laser Raman spectroscopy. The LOI value of HD/FR/Z-0.5 composite with an optimum content of 0.5 wt. % zeolite 4 A and 25 wt. % of total flame retardant reaches 26.3 %. A low loading of zeolite 4 A can improve the bench-scale combustion performance as determined by cone calorimetry, and promote the formation of more compact char residue with a highly graphitic structure. However, a low loading of zeolite in combination with the IFR system consisting of APP and THEIC produces no significant changes in mechanical performance.

Preparation, structure and flame retardancy of poly(butylene terephthalate) with gradient intumescent flame retardant distribution

In this manuscript, the content-gradient distributions of an intumescent flame retardant (IFR) island-shaped structure in poly(butylene terephthalate) (PBT) were prepared using compression sintering processing technology inspired by powder metallurgy, to achieve efficient flame retardancy and mechanical properties with low flame retardant dosage. The PBT/IFR master-batch was first prepared by extrusion and then pulverized into powder. At low temperature (20 °C below the melting temperature) and high pressure (≥ 50 MPa) sintering processing conditions, two PBT/IFR powders with different levels of IFR content were fabricated into restricted island-like structure composites. The island with a higher IFR content exhibited flame retardancy, while the island with lower IFR content maintained the mechanics of the matrix. Compared with the uniform dispersion PBT/20 wt% IFR composite, the combustion of the PBT/IFR (25 wt%:15 wt% = 1:1) gradient content composite improved from V-1 to V-0 using a UL-94 test, while the tensile strength increased by 10%. The performance of the flame retardant was improved by periodically changing its distribution in the polymer matrix via restricted island-like structures fabricated using compression sintering processing technology inspired by powder metallurgy.

Investigation of the Flammability and Thermal Stability of Halogen-Free Intumescent System in Biopolymer Composites Containing Biobased Carbonization Agent and Mechanism of Their Char Formation.

Starch, being a polyhydric compound with its natural charring ability, is an ideal candidate to serve as a carbonization agent in an intumescent system. This charring ability of starch, if accompanied by an acidic source, can generate an effective intumescent flame retardant (IFR) system, but the performance of starch-based composites in an IFR system has not been tested in detail. Here, we describe a PLA-based IFR system consisting of ammonium polyphosphate (APP) as acidic source and cornstarch as carbon source. We prepared different formulations by melt compounding followed by molding into sheets by hot pressing. The thermal behavior and surface morphology of the composites was investigated by thermogravimetric analysis and scanning electron microscopy respectively. We also conducted limiting oxygen index (LOI), UL-94, and cone calorimetry tests to characterize the flame-retardant properties. Cone calorimetry revealed a 66% reduction in the peak heat release rate of the IFR composites compared to pure PLA and indicated the development of an intumescent structure by leaving a residual mass of 43% relative to the initial mass of the sample. A mechanism of char formation has also been discussed in detail.

MoO3-ZrO2 solid acid for enhancement in the efficiency of intumescent flame retardant

To further improve the efficiency of intumescent flame retardant (IFR) system consisting of ammonium polyphosphate and charring-foaming agent, MoO3-ZrO2 solid acid is used as an adjuvant. The influence of MoO3-ZrO2 on the thermal decomposition, reaction to small flame and fire behavior of polypropylene (PP)/IFR composite is investigated. The incorporation of 1 wt% solid acid results in the enhanced limiting oxygen index (LOI) and fire safety of PP/IFR composite, while decreasing its peak heat release rate from 431 to 370 kW/m2. Flame retardant mechanism is proposed based on the analysis of thermal decomposition behavior and char residue. The yield and graphitization degree of char residue are improved by MoO3-ZrO2. The release of CO2 from thermal decomposition of IFR is accelerated by this solid acid. This work provides a new path to designing highly fire retardant polymer composites.

Effect of novel intumescent flame retardant on mechanical and flame retardant properties of continuous glass fibre reinforced polypropylene composites

In this study, the influence of a novel intumescent flame retardant (IFR) on the mode I interlaminar fracture toughness and flame retardant properties of continuous glass fibre reinforced polypropylene (CGF/PP) composites is presented. The novel IFR system that consists of ammonium polyphosphate/poly (ethanediamine-1, 3, 5 triazine-o-4-amion-2, 2, 6, 6- tetramentylniperidine) (APP/PETAT) was introduced into the CGF/PP unidirectional prepregs (UD) composites by hot-melt impregnation process. Double cantilever beam (DCB) tests were performed to evaluate the mode I interlaminar fracture toughness (GIC) by using modified beam theory (MBT). It was found from the experimental results that compared to the neat CGF/PP composite, the mode I fracture toughness initiation toughness (GIC init.) and propagation toughness (GIC prop.) of CGF/PP/12.5 wt% IFR composites were increased by an average of 99.7% and 119.11% respectively. Meanwhile, samples with 12.5 wt% IFR could self-extinguish with an oxygen concentration of 32.4% and exhibit lower fire spread speed in UL-94 test. Furthermore, the peak of heat release rate (PHRR), total heat release (THR), fire performance index (FPI), and mass loss rate (MLR) tests indicated that IFR could dramatically enhance the flame retardancy of the composites.

Synergistic effect of multiwalled carbon nanotubes and an intumescent flame retardant: Toward an ideal electromagnetic interference shielding material with excellent flame retardancy

ABSTRACTTo shield undesirable electromagnetic waves caused by electronic devices and simultaneously resolve the flame safety of the electronic components, an electromagnetic interference (EMI) shielding material with excellent flame‐retardant properties is urgently needed. The synergistic effect of the intumescent flame retardant (IFR) and multiwalled carbon nanotubes (MWCNTs) for polystyrene (PS) nanocomposites prepared by melt blending was investigated. The results show that addition of certain amounts of IFRs facilitated the dispersion of MWCNTs in the PS matrix, and the percolation threshold of the MWCNTs in the PS matrix also decreased from 1.67 ± 0.05 to 1.29 ± 0.04 wt %. Moreover, the EMI shielding efficiencies (SEs) of the PS–MWCNT–IFR composites were consistently higher than those of the PS–MWCNT composites without the addition of the IFRs at the same MWCNT content; this indicated that the synergistic effect of the MWCNTs and IFRs effectively improved the EMI SE of the PS–MWCNT–IFR composites. Furthermore, the limiting oxygen index (LOI) testing results show that the LOI values of the PS–MWCNT composites were consistently higher than 27%; this indicated that the PS–MWCNT composites effectively met the needs of flame safety; this indicated that the PS–MWCNT–IFR composite is a novel and promising candidate for an ideal EMI shielding material with excellent flame‐retardant properties for today's electronic devices. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45088.

Effects of surface acid-activated kaolinite on the fire performance of polypropylene composite

Modified kaolinite containing Lewis acidic sites (Acid-Kaol) was prepared by calcination of kaolinite (Kaol) and successive acid treatment. Acid-Kaol was then introduced into polypropylene (PP) with intumescent flame-retardant (IFR). The flammability and thermostability of PP/IFR/Acid-Kaol were studied by limiting oxygen index (LOI), vertical buring test (UL-94), cone calorimeter test (CCT) and thermogravimetric analysis (TGA). LOI value of PP/25wt.% IFR composite was 31.1%, it increased to 34.9% by 1.5wt.% Acid-Kaol substitution with IFR. Moreover, the peak of heat release rate (PHRR) of PP/IFR/Acid-Kaol decreased 46.8% compared with that of PP/IFR composite. The residues after CCT were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectrometer (XPS) and FTIR. It was indicated that Acid-Kaol accelerated crosslinking during combustion and promoted char formation, which will act as insulating barrier to protect the matrix from further decomposed.

Modelled decomposition mechanism of flame retarded poly(vinyl acetate) by melamine isocyanurate

Model polymer poly(vinyl acetate) (PVAc) was combined with melamine isocyanurate (MIC) as intumescent flame retardant composite. This work emphasises on the study of the decomposition mechanism and compared with a single fire test in order to show its performance as flame retarded composite. As such, mass loss cone calorimetry tests were performed and compared with it inert and oxidative decompositions in lab tests. PVAc/MIC composites cannot be ignited with high loadings MIC. Difference curves in oxidative conditions revealed that the composites with MIC show only positive differences, indicating a high stabilisation, especially in the temperature region of a mild flame (500–700 °C). Experiments performed with TG coupled with mass spectroscopy and analyses on partially degraded residues with solid-state 13C-NMR enabled the construction of the complete decomposition mechanism. MIC has both a heat-sink FR activity as well as a crosslinking role in the stabilization of the polymer. The latter then creates a highly stabilised char at elevated temperatures in oxidative environments. The formed char starts to degrade only 100 °C higher than the pure polymer within a heating. The degradation of formed char of pure PVAc is autocatalytic; this behaviour disappears upon addition of sufficient amount of MIC. Therefore, the transport of fuel towards the gaseous phase is limited, creating an efficient flame retardant system.

Synergistic flame retardant effects of composites containing organic montmorillonite, Nylon 6 and 2-cyclic pentaerythritoloctahydrogen tetraphosphate-4,6-benzene sulfonic acid sodium ammion-triazine

A novel P-N containing intumescent flame retardant, 2-cyclic pentaerythritoloctahydrogen tetraphosphate-4,6-benzene sulfonic acid sodium ammion-triazine (CTOB) was synthesized and used as an additive in intumescent flame retardant composites containing organic montmorillonite (OMMT) and Nylon 6. The thermal stability and flammability properties of Nylon 6, CTOB, OMMT and their composites were investigated by TGA, limiting oxygen index (LOI) and cone calorimeter tests. Synergistic effects between CTOB and OMMT in the Nylon 6/CTOB/OMM composite were observed. A combination of CTOB and OMMT improved the thermal stability and the flammability properties of Nylon 6 and increased the LOI value to 28.0%. The average and peak heat release rates of the ternary composite were reduced by about 65.7 and 49.3%, respectively, compared with those of Nylon 6. The residue generated after the cone calorimeter tests upon combustion of the ternary composite was a compact and dense char as revealed by SEM, which is critically important for an excellent flame retardant.

Effects of ammonium polyphosphate to pentaerythritol ratio on composition and properties of carbonaceous foam deriving from intumescent flame-retardant polypropylene

In our work, a classical system was used for intumescent flame retardant (IFR), consisting of ammonium polyphosphate (APP) and pentaerythritol (PER). Effects of weight ratio of APP to PER (APP-PER ratio) on various aspects of carbonaceous foam deriving from polypropylene (PP)/IFR composites were investigated. Tested parameters included the flame retardancy and composition, as well as the structural and thermophysical properties of the carbonaceous foam. The carbonaceous foam resulting from PP/IFR composites was a physical mixture of phosphorous degradation products (PDPs) and insoluble chars. The structural and thermophysical properties of the carbonaceous foam affected by the APP-PER ratio include its expansion ratio, air tightness, thermal conductivity and thermal diffusivity. These properties in turn affected the efficiency of both mass (O2 and combustibles) and heat transfer between the gas and the condensed phases. The content of PDPs in the mixed melt during the foaming stage and in the solidified carbonaceous foam was considered as the main regulator of these important properties of the carbonaceous foam. Concise heat and mass transfer theories were applied to qualitatively explain the results of flame retardant tests.

Synergistic Effect of SiO2 on Intumescent Flame-retardant Polypropylene

The flammability of polypropylene and its intumescent flame retardant composites consisting of ammonium polyphosphate (APP), pentaerythritol (PER) and SiO2 were studied and the synergistic effect of SiO2, as well as the synergistic mechanism was discussed in detail. For the composites, the content of SiO2 varied from 0 to 12 wt.% where the total addition of APP/PER/SiO2 was constant at 30 wt.%. The flammability properties were characterized by Limiting Oxygen Index (LOI) and UL-94 tests, while the synergistic mechanism of SiO2 was investigated by a combination of thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectrometry and scanning electron microscopy (SEM). The results showed that SiO2 had a synergistic effect on the PP/APP/PER system, with an optimum addition at 3.5 wt.%. The introduction of SiO2 improved the flame retardant properties of the PP/APP/PER system and the strength of the char layer.

Influencing Mechanism of Transition Metal Oxide on Thermal Decomposition of Ammonium Polyphosphate

Transition metal oxide (MO) can obviously influence the thermal decomposition process of ammonium polyphosphate (APP) to improve the flame retardant efficiency of intumescent flame retardant composites based on APP in polymer. ZnO, Fe2O3 and TiO2, in same amount were added into APP to study the influence of MO on thermal decomposition behavior of APP, and to analyze the evolution of chemical state of metallic atoms and phosphorus atom and crystal structure in the interaction processes by thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD) respectively. TGA and XPS spectra showed that MO could catalyze the releasing of NH3 and H2O of APP in the earlier period, and increase the high temperature residue in the later period due to the formation of metallic phosphate. The sequence of catalytic activity for the process of releasing of NH3 and H2O was as follows: ZnO>Fe2O3>TiO2, and that of cross-linking ability for thermal decomposition product P-O of APP was as follows: Fe2O3>ZnO>TiO2. XRD showed that APP could react with ZnO, Fe2O3 and TiO2 to produce Zn(PO3)(2), Fe-4(P2O7)(3) and TiP2O7, respectively, at high temperature.

Flame Retardant Mechanism of a Novel Intumescent Flame Retardant Polypropylene

Abstract A novel intumescent flame retardant was incorporated into polypropylene to prepare novel intumescent flame retardant composites (PP/IFR) with good flame retardant properties. The flame retardant mechanism was investigated by means of Laser Raman spectroscopy (LRS), X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis/infrared spectrometry (TGA-IR), Fourier Transform infrared spectroscopy (FTIR) and Energy Dispersive Spectrometer (EDS). It was found that the IFR could decrease the degradation rate of PP; the formed intumescent char was containing unorganized carbon structure and graphitic structure, and consisting of P, N, O and C elements. FTIR analysis showed that the network with P-O-P and P-O-C were formed. EDS analysis results revealed that some P elements were connected to the polyaromatic rings and could form huge connected network.

Preparation and Properties of Flame Retardant Polypropylene with an Intumescent System Encapsulated by Thermoplastic Polyurethane

A novel intumescent flame retardant (IFR), using thermoplastic polyurethane (TPU) as a carrier resin to encapsulate melamine pyrophosphate/pentaerythritol (MPP/PER), was adopted to flame retard polypropylene (PP). The effects of TPU encapsulation on the mechanical properties, flame retardancy, thermal stability, and water-resistance of flame retardant PP were investigated. It was found that the dispersion of the IFR particles and the compatibility between the IFR and PP matrix were improved, which was responsible for the enhanced mechanical properties and flame retardancy of the flame retardant PP. Moreover, the incorporation of TPU could effectively prevent the esterification reaction between MPP and PER during the processing of flame retardant PP, and prevent the IFR from leaching out of the PP matrix. It thus remarkably improved the thermal stability and water-resistance of the IFR. Furthermore, PP/TPU-encapsulated IFR composite showed better charring performance than that of PP/MPP/PER.

Synthesis and Flame Retardant Properties of Melamine Modified EH Lignin

A novel intumescent flame retardant (IFR), melamine modified enzymatic hydrolysis lignin (MEHL), was synthesized and well characterized by FTIR and TGA. The results showed that the decompose temperature of MEHL is much higher than that of enzymatic hydrolysis lignin (EHL). In order to improve flame retardancy and dripping resistance of EPDM, MEHL and microencapsulated red phosphorus (MRP) were added into EPDM as IFR system. The flame ability and thermal stability of IFR and EPDM composites were investigated by UL-94 vertical burning test and LOI measurements. The results indicated that FV-0 was reached and the LOI value was 35 when per hundred rubber (phr) together with 12 phr MRP and 50 phr EHLM were added. SEM photos showed that the char residue was continuous, and a barrier between flame and rubber was formed, while there were also small holes in its surfaces. On all accounts, EHL used as a carbonization agent instead of petroleum chemicals, such as pentaerythritol, was more environmental friendly and beneficial to economy.

Effect of an Ultrahigh Rubber ABS Impact Modifier Resin on Mechanical Properties of Intumescent Flame-Retardant ABS Composites

The effect of an ultrahigh rubber acrylonitrile-butadiene-styrene (ABS) impact modifier resin (UHR-ABS) on the mechanical properties of an intumescent flame-retardant ABS composite was characterized. Samples were obtained by compounding ABS and an intumescent flame-retardant master batch that was prepared using an intumescent flame-retardant composite (IFRC) with ABS and/or UHR-ABS as well as by direct compounding IFRC, UHR-ABS, and ABS. The incorporation of UHR-ABS resulted in reduction in the storage modulus, damping behavior and glass transition temperature, as evidenced by dynamic mechanical analysis. With increasing mass fraction of the UHR-ABS, the tensile strength and the flexural strength decreased gradually, and the notched impact strength increased, but the increase was more significant for compounding IFRC, UHR-ABS, and ABS than for compounding ABS and IFRC master batches. SEM micrographs of the fresh fracture surface of the composites were used to estimate the mechanism of the increased notched impact strength owing to the incorporation of UHR-ABS.

Thermal Degradation and Combustion Behavior of a Modified Intumescent Flame-retardant ABS Composite

With the aim of improving compatibility between intumescent flame-retardant (IFR) acrylonitrile—butadiene—styrene (ABS) composites, we have prepared a modified intumescent flame-retardant composite (IFRC) powder by compounding the three components of the IFR normally used with TX-10 surfactant/polyacrylate latex. The ABS/IFRC composites were compared with the unfilled ABS by investigating their thermal degradation and combustion behaviors with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and a cone calorimeter (CONE). The DSC and TGA data showed that the thermal stability of the ABS/IFRC at high temperature could be enhanced and the char residue formation was effectively increased by comparison with the ABS. The CONE results revealed that IFRC was clearly able to change the decomposition behavior of ABS and form a char layer on the surface of the composites, resulting in an efficient reduction of their flammability parameters compared with the ABS, such as the heat release rate, total heat release, rate of smoke release, total smoke release, and so on.

Flame Retardancy and Thermal Degradation of Intumescent Flame Retardant Starch-Based Biodegradable Composites

Biodegradable PVA/glycerol-plasticized thermoplastic starch (TPS) and its intumescent flame retardant composites are prepared. Microencapsulated ammonium polyphosphate (MCAPP) was used not only to utilize the charring capacity of the polyhydric compounds but also to restrain the reaction between APP and starch during processing. The flame retardancy and thermal stability of TPS and TPS/MCAPP were characterized by LOI, UL 94, TG, and microscale combustion calorimeter (MCC). TPS/MCAPP composites with only 2 wt % MCAPP can pass V-0 in UL 94 test. However, neat TPS cannot pass any rating. The presence of MCAPP can reduce the total heat release of TPS sharply in MCC test. The thermal degradation and gas products of TPS and TPS/MCAPP were monitored by TG-FTIR and dynamic FTIR. XPS and SEM measurements were utilized to investigate the chemical structure, as well as the surface morphology of the residual char.